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Optimal design of the transmission-way of mechanical stress throughthe interface between a joint prosthesis and bone tissue together with the criterion formulation for the assessment of the fixation method

关节假体与骨组织界面机械应力传递方式的优化设计及固定方法评估标准的制定

基本信息

批准号：
20560086
负责人：
MABUCHI Kiyoshi
金额：
$ 3.08万
依托单位：
Kitasato University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2010
项目状态：
已结题

项目摘要

Failure criteria of ultra-high molecular weight polyethylene (UHMWPE) should be clarified for the strength design of joint prostheses. In the present study, we performed compression tests of UHMWPE plates together with finite element (FE) analysis under conditions similar to those within a total knee prosthesis and discuss the failure criteria.Flat plates made of conventional or cross linked UHMWPE were molded as test pieces. Those thicknesses were ranging from 2 mm to 8 mm. The compression test using a loading machine was performed in a bath filled with saline solution at 37 degrees centigrade. A metallic sphere 50 mm in diameter was used for the indenter. The load was applied to 6 kN under a crosshead speed of 2 mm per minute. Flow pressure was calculated after the test as a ratio of the impressio area and the maximum load. Deformation of the plate was estimated by displacement at the edge. Additionally, the FE analysis was performed on a virtual model using the same conditions as in … More the experiments.The values of the flow pressure were measured as a mean of 32.8 MPa, SD 2.3 MPa for conventional UHMWPE, and as a mean of 37.3 MPa, SD 0.9 MPa for cross-linked UHMWPE. The displacement of the UHMWPE plate increased with decreasing thickness of the plate. The displacement estimated by FE analysis was similar to that of theexperimental findings. Furthermore, shear strain in the UHMWPE plate of FE model increased with the displacement. It was concluded that the failure criteria of joint prostheses must be presented by not only the stress but also the strain in a UHMWPE insert.Stress in bone tissue must be remained after the press-fit-fixation of a implant. The residual stress must bring on the biological response around the implant. The effect has not been sufficiently discussed, yet, because the residual stress is stationary and unlike the physiological mechanical conditions.In the present study, we developed a method to configure stationary stress field in a rat femur using a pin with the hyper elasticity. As the results, it was observed that bone hypertrophy emerged at the fringe of the femur under six weeks stationary load from the pin inside bone marrow. Less

关节假体的强度设计应明确超高分子量聚乙烯（UHMWPE）的失效准则。在本研究中，我们在类似于全膝关节假体的条件下进行了 UHMWPE 板的压缩测试和有限元 (FE) 分析，并讨论了失效标准。由传统或交联 UHMWPE 制成的平板被模制成测试件。这些厚度范围从 2 毫米到 8 毫米。使用加载机的压缩试验在充满37℃的生理盐水的浴中进行。压头使用直径50mm的金属球。在每分钟 2 毫米的十字头速度下施加 6 kN 的负载。测试后计算流动压力作为压痕面积与最大负载的比率。通过边缘处的位移来估计板的变形。此外，使用与实验相同的条件在虚拟模型上进行有限元分析。传统 UHMWPE 的流动压力平均值为 32.8 MPa，SD 2.3 MPa，交联 UHMWPE 的平均值为 37.3 MPa，SD 0.9 MPa。 UHMWPE板的位移随着板厚度的减小而增加。有限元分析估计的位移与实验结果相似。此外，有限元模型的 UHMWPE 板中的剪切应变随着位移的增加而增加。结论是，关节假体的失效标准不仅必须由 UHMWPE 插入物中的应力来表示，还必须由 UHMWPE 插入物中的应变来表示。在植入物压配合固定后，骨组织中必须保留应力。残余应力必须引起植入物周围的生物反应。然而，这种效应尚未得到充分讨论，因为残余应力是固定的，与生理力学条件不同。在本研究中，我们开发了一种使用具有超弹性的销钉在大鼠股骨中配置固定应力场的方法。结果，观察到在骨髓内的钉施加六周的固定负载的情况下，股骨边缘出现骨质肥大。较少的